Thermal Container Including a Thermal Unit

ABSTRACT

In some embodiments, a thermal container may include a thermal tank, a cold source reservoir, and a tube forming a closed loop in contact with the thermal tank and with the cold source reservoir and configured to secure a thermal fluid. The thermal fluid may have a freeze temperature that is below zero degrees Celsius. The thermal container may further include a pump coupled to the tube and configured to circulate the thermal fluid between the cold source reservoir and the thermal tank when a temperature of the thermal tank exceeds a selected temperature. In some embodiments, the thermal container may further include a heating element coupled to the thermal tank and configured to apply heat to the thermal tank when the temperature falls below the selected temperature by more than a threshold amount.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present disclosure is a non-provisional of and claims priority to U.S. Provisional Patent Application No. 62/188,562 filed on Jul. 3, 2015 and entitled “Thermal Container Including a Thermal Unit”, which is incorporated herein by reference in its entirety.

FIELD

The present disclosure is generally related to thermal container devices, such as portable, insulated thermal containers, and more particularly to portable thermal container devices having a thermal unit that is isolated from food items within a thermal tank and that can provide heating, cooling, or both.

BACKGROUND

Portable thermal containers may include a chilled tank or compartment, which may be stocked with food items or beverages and which may include ice, cold packs or other items. Some portable thermal containers may be used for transporting other items, such as organs for transplant operations, and so on. In general, such thermal containers may be carried by hand or may include wheels and a handle by which may the thermal container to be pushed or otherwise moved around. Such thermal containers may be insulated containers configured to passively maintain a temperature of items within the enclosure relative to the ambient temperature of the surroundings and sometimes with the assistance of a cold source, such as ice.

SUMMARY

In some embodiments, a thermal container may include a thermal tank, a cold source reservoir, and a tube forming a closed loop in contact with the thermal tank and with the cold source reservoir and configured to secure a thermal fluid. The thermal fluid may have a freeze temperature that is below zero degrees Celsius. The thermal container may further include a pump coupled to the tube and configured to circulate the thermal fluid between the cold source reservoir and the thermal tank when a temperature of the thermal tank exceeds a selected temperature. In some embodiments, the thermal container may further include a heating element coupled to the thermal tank and configured to apply heat to the thermal tank when the temperature falls below the selected temperature by more than a threshold amount. Alternatively, the thermal container may include a reverse flow valve configured to reverse coolant flood flow when the thermal tank falls below a selected temperature.

In some embodiments, an apparatus may include a thermal unit sized to fit within a portable thermal container defining an enclosure, such as a portable cooler. The thermal unit may include an interface to receive a selected temperature, one or more temperature sensors, and a control circuit coupled to the interface and the one or more temperature sensors. The control circuit may be configured to selectively control one of a heating element and a cooling element to maintain a temperature of the enclosure within a range of the selected temperature.

In some embodiments, the thermal unit may include a control circuit configured to control the pump to control one of a heating element and a flow rate of a thermal fluid to maintain a selected temperature of an enclosure. In some embodiments, the thermal unit can include an input/output (I/O) interface coupled to the control circuit and configured to receive input data, such as a temperature setting, from a touchscreen, a keypad, or an external electronic device, such as a smartphone or other computing device.

In still other embodiments, a method may include receiving a temperature setting. The method may also include determining a temperature of a thermal tank and selectively adjusting a flow rate of a chill fluid extending between a cold source and the thermal tank to maintain the temperature of the thermal tank according to the temperature setting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a thermal container, in accordance with certain embodiments of the present disclosure.

FIG. 1B is a top view of the thermal container of FIG. 1A including an open lid, in accordance with certain embodiments of the present disclosure.

FIG. 2A is a perspective view of a thermal container including an interface to control a chill temperature, in accordance with certain embodiments of the present disclosure.

FIG. 2B is a top view of the thermal container including an open lid and including an interface to control a chill temperature, in accordance with certain embodiments of the present disclosure.

FIG. 3 is a block diagram of a thermal container, in accordance with certain embodiments of the present disclosure.

FIG. 4 is a block diagram of an apparatus including a thermal unit, which may be inserted in an enclosure, in accordance with certain embodiments of the present disclosure.

FIG. 5 is a flow diagram of a method of operating a thermal container, in accordance with certain embodiments of the present disclosure.

FIG. 6 is a flow diagram of a method of operating a thermal container, in accordance with certain embodiments of the present disclosure.

In the following discussion, the same reference numbers are used in the various embodiments to indicate the same or similar elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of a thermal unit are described below, which may include a cold source reservoir that is isolated from the items to be chilled. In some embodiments, the cold source reservoir may include dry ice or another cold source, and the thermal unit may include a pump configured to circulate a fluid about a cold source reservoir to chill the fluid and to circulate the chilled fluid around a thermal tank to cool the items to be chilled. The fluid may include a thermal fluid that may maintain its fluid, viscous phase at temperatures below −109° Fahrenheit (F.),i.e., below −79° Celsius (C.), which is the freeze temperature of dry ice. In a particular embodiment, the thermal fluid may include propylene glycol, which is a viscous colorless liquid that is nearly odorless but which possesses a faintly sweet taste. Chemically, propylene glycol may be classified as a diol and is miscible with a broad range of solvents, including water, acetone, and chloroform. Propylene glycol is sometimes uses in food processing as the E-number E1520 and is sometimes called α-propylene glycol to distinguish it from the isomer propane-1,3-diol (β-propylene glycol). In some embodiments, the thermal fluid may be an oil or other food safe fluid, such as a mineral oil or other fluid. The thermal fluid may be selected from a variety of different fluids based on heat transfer characteristics that allow the fluid to be chilled to a temperature that may be below a freeze temperature of water (i.e., below 32° F. or 0° C.) without changing phase. If dry ice is used as the cold source, the thermal fluid should be selected to have a freeze temperature that is below that of dry ice, i.e., below 109° F.

In some embodiments, the thermal unit may further include a plurality of temperature sensors. Additionally, the thermal unit may include a control circuit coupled to the pump and to the plurality of temperature sensors. In some embodiments, the thermal unit may control the pump to adjust a flow rate of the thermal fluid to cool the thermal tank to a selected temperature.

In some embodiments, the thermal unit may further include a heating element, which may be coupled to or which may extend round or near the thermal tank to radiate heat. In some embodiments, the control circuit may be coupled to the heating element and may be configured to selectively control the heating element to deliver heat to the thermal tank when a temperature of the thermal tank falls below a threshold temperature. In some embodiments, the control circuit may selectively activate the heating element to radiate heat when the measured temperature is below the selected temperature and when a difference between the selected temperature and the measured temperature of the thermal tank is greater than a threshold. Other embodiments are also possible. One possible example of a thermal container is described below with respect to FIG. 1A.

FIG. 1A is a perspective view of a thermal container 100, in accordance with certain embodiments of the present disclosure. The thermal container 100 may include a housing 102 defining an enclosure sized to receive items to be chilled, and may include a lid 104, which may be coupled to the housing 102 by a hinge or seal. In some embodiments, the hinge may be formed from interlocking elements on the housing 102 and the lid 104. In other embodiments, the hinge may be attached to the housing 102 and the lid 104.

In some embodiments, the thermal container 100 may include a thermal unit, which may be configured to selectively apply heat or cold to a thermal tank to maintain the thermal tank at a selected temperature. In some embodiments, the thermal container may include a pump configured to circulate a thermal fluid from a cold source reservoir to a thermal tank and back to provide a cooling effect to the thermal tank. The thermal container 100 may further include a control circuit coupled to the pump to control a rate of the flow of the thermal fluid. The control circuit may also be configured to selectively activate a thermal element to radiate heat to increase a temperature of the thermal tank. In some embodiments, the thermal unit may include or be coupled to a plurality of temperature sensors, and the controller may selectively activate one of the pump and the heating element in response to a measured temperature.

FIG. 1B is a top view 120 of the thermal container 100 of FIG. 1A including an open lid 104, in accordance with certain embodiments of the present disclosure. The housing 102 defines an enclosure 103, which is sized to include a cold source reservoir 124 and a chilled tank 122. The lid 104 may be hinged or otherwise coupled to the housing 102 and configured to be closable to provide a sealed enclosure. In some embodiments, the chilled tank 122 may be spaced apart from the cold source reservoir 124, and a thermal fluid may be used to transfer the cold to the chilled tank 122 and to carry heat from the chilled tank 122. The thermal fluid may be selected from a variety of fluids to transfer heat or cold to and from the thermal tank 122. In some embodiments, the thermal fluid may include propylene glycol.

The cold source reservoir 124 may include a removable lid to allow access for insertion of a cold source, such as dry ice. The cold source reservoir 124 may be thermally insulated to maintain the temperature of the cold source. Further, tubing for circulation of the thermal fluid may be insulated to prevent thermal dissipation and to ensure delivery of the chilled fluid to the thermal tank 122. Additionally, insulation may be provided around the tubing and the thermal tank 122 to preserve the cold temperature in the thermal tank 122.

In some embodiments, the thermal container 100 may include a tube or pipe formed from a material that may allow for heat transfer, which tube or pipe may provide a conduit for a thermal fluid (e.g., propylene glycol). In some embodiments, the tube or pipe may be wrapped around a circumference of the cold source reservoir 124 to chill the thermal fluid and may be wrapped around or in contact with at least a portion of the thermal tank 122 to deliver the cold from the thermal fluid to the thermal tank 122. In some embodiments, the tube or pipe may be flexible and may be arranged along a bottom portion of the thermal tank 122 (outside of the thermal tank 122). The tube or pipe may then extend back to the cold source reservoir 124 to be chilled again. In some embodiments, the thermal container 100 may include a pump coupled to the tube or pipe and configured to circulate the thermal fluid through the tube. Further, in some embodiments, the thermal container 100 may include a control circuit to maintain a selected temperature in the thermal tank 122. Additionally, in some embodiments, the thermal unit may include a heating element coupled to the thermal tank 122, which heating element may be selectively activated by a control circuit. In some embodiments, the control circuit may selectively control the pump and the heating element to maintain the thermal tank 122 at a selected temperature setting.

In some embodiments, the control circuit may be coupled to an interface, which may include a display and a keypad (or which may couple to a computing device, such as a smart phone, a tablet computer, or another computing device) and which may be accessed by a user to configure the selected temperature. One possible example of a thermal container including an interface is described below with respect to FIG. 2A.

FIG. 2A is a perspective view of a thermal container 200 including an interface 206 to control a chill temperature, in accordance with certain embodiments of the present disclosure. The thermal container 200 may include a housing 202 coupled to a lid 204. The housing 202 and the lid 204 may define an enclosure sized to receive items to be cooled. The thermal container 200 may include all of the elements of the thermal container 100 in FIGS. 1A and 1B, and may include the interface 206 on an external surface of the lid 204.

In some embodiments, the interface 206 may include a touchscreen interface or a display and a keypad. In some embodiments, the interface 206 may include a port or connector, which may be coupled to a computing device, such as a smart phone, a laptop computer or a tablet computer. In some embodiments, the interface 206 may include a transceiver configured to communicate wirelessly with a computing device, such as a smart phone, a laptop computer or a tablet computer.

In some embodiments, a user may access the interface 206 to program a temperature of the thermal container 200. A control circuit coupled to the interface 206 may monitor one or more temperature sensors associated with a thermal tank within the thermal container 200 and may selectively adjust fluid flow between the cold source reservoir and the thermal tank to maintain the temperature of the thermal tank according to the selected temperature. In some embodiments, the control circuit may maintain the temperature within a temperature range around the selected temperature. In a particular embodiments, if the temperature of the thermal tank falls below a threshold temperature, which may be defined as a delta relative to the selected temperature, the control circuit may reverse the flow of the thermal fluid to warm the thermal tank or may reduce the rate of flow of the thermal fluid to prevent the thermal tank from becoming too cold.

FIG. 2B is a top view 220 of the thermal container 200 including an open lid 204 and including an interface 226 to control a chill temperature, in accordance with certain embodiments of the present disclosure. In the illustrated embodiment, the thermal container 200 may include a thermal tank 222 and a cold source reservoir 224. Further, the thermal container 200 may include an interface 226 inside of the thermal container 200, instead of or in addition to the interface on the surface of the lid 204.

In some embodiments, the interface 226 may include a display (in this case indicating a selected temperature of 45° F.) and a keypad. The interface 226 may be accessed to program a selected temperature of the thermal tank 222, which temperature may be maintained by controlling a rate of flow of a thermal fluid between the cold source reservoir 224 and the thermal tank 222. In some embodiments, the interface 226 may allow a user to configure settings to adjust the rate of fluid flow based on at least one of a temperature of the thermal tank, an outside temperature, a time of day, and another parameter. In some embodiments, the interface 226 may provide information corresponding to a power level of a battery or other power source configured to deliver power to the control circuit and other components of the thermal unit. In a particular illustrative example, the interface 226 may include a power level indicator, such as a light emitting diode, an audio indicator, another detectable indicator, or any combination thereof, to alert a user that a power level of a power source is low and may require recharge or replacement.

In the illustrated example, the lid 204 may be configured to seal to the housing 202 to define the enclosure. In other embodiments, the lid 204 may include a first portion configured to form a seal with the thermal tank 222 and a second portion configured to fit over the cold source reservoir 224 and the interface 226. In some embodiments, a portion of the lid 204 may include a vent or a one-way valve for heat and gas pressure dissipation. Other embodiments are also possible.

In the illustrated embodiment, the thermal tank 222 is approximately ⅔rds of the volume of the enclosure within the housing 222 and the cold source reservoir 224, the interface 226, and associated circuitry and tubes may occupy approximately ⅓^(rd) of the volume of the enclosure. However, in other embodiments, the thermal tank 222 may be expanded to occupy a larger percentage of the volume of the enclosure. In some embodiments, the thermal tank 222 may occupy approximately ⅚ths of the volume of the enclosure. In some embodiments, the cold source reservoir 224, circuitry, pump, and interface 226 may occupy a volume of approximately 10 cubic inches or less, and the thermal tank 222 may occupy a remaining volume of the enclosure. In some embodiments, the volume of the cold sourcing portion of the apparatus may be scaled based on the size of the thermal tank 222.

FIG. 3 is a block diagram of a thermal container 300, in accordance with certain embodiments of the present disclosure. The thermal container 300 may be an embodiment of the thermal container 100 of FIGS. 1A and 1B or of the thermal container 200 of FIGS. 2A or 2B. The thermal container 300 may include a cold source reservoir 302 including an enclosure 304 sized to receive a cold source, such as dry ice or another cold source. The cold source reservoir 302 may include an insulated body portion. A thermally conductive tube 306 may be wrapped or coiled about the cold source reservoir 302 and may be coupled to a thermally insulated tube 307, which may extend to a thermal tank 308 defining an enclosure 310. The thermal tank 308 may include an insulated body portion, which may be wrapped by a thermally conductive coil 312 coupled to the tube 307.

In some embodiments, the thermal container 300 may include a reverse flow valve 309 that may be controlled by a control circuit 318 by a control signal sent via a control line (not shown) to enable reverse fluid flow from the thermal tank 308 to the cold source reservoir 302 when the ambient temperature or the temperature in the thermal tank 308 falls below a threshold. In an example, the reverse flow valve 309 may prevet the tube 307 from freezing and the thermal tank 308 from damaging its contents.

The thermal container 300 may further include a cold fluid reservoir 314 coupled to the thermally conductive coil 312 by a tube 313, which may or may not be insulated. The cold fluid reservoir 314 may be coupled to a pump 316 by a tube 315, and the pump 316 may be coupled to a tube 317 that is coupled to the thermally conductive tube 306. The pump 316 may also be electrically coupled to a control circuit 318. In some embodiments, the thermal container 300 may include one or more pumps.

In some embodiments, the control circuit 318 may be coupled via a multiplexer 322 to one or more sensors 320 (labeled “S”), which may be coupled to the thermal tank 308. Further, the control circuit 318 may be coupled to an external temperature sensor 321 via the multiplexer 322. In some embodiments, the control circuit 318 may provide a selection signal to the multiplexer 322 to selectively determine a temperature from one or more of the sensors 320 and 321. In some embodiments, the control circuit 318 may monitor the temperature periodically.

In some embodiments, the control circuit 318 may be coupled to an input/output (I/O) interface 324. The I/O interface 324 may be coupled to a display 326 and a keypad 328. In some embodiments, the display 326 and the keypad 328 may be combined in a touchscreen interface. In some embodiments, the I/O interface 324 may be communicatively coupled via a wired or wireless connection to an external electronic device 332, such as a remote control circuit, a smart phone, a tablet computer, a laptop computer, another computing device, or any combination thereof. In some embodiments, the electronic device 332 may configure temperature settings of the thermal container 300, and the control circuit 318 may be configured to selectively control the pump 316 to manage a rate of fluid flow between the cold source reservoir 302 and the thermal tank 308 based on the selected temperature settings. The control circuit 318 may also be coupled to a heating element 336, which may be selectively activated by electrical signals from the control circuit 318 to radiate heat for warming the thermal tank 310.

In certain embodiments, the electronic device 332 may be a computing device, such as a smartphone, a tablet computer, a laptop computer, or another computing device. In an example, the control circuit 318 may communicate data to the electronic device 332 through a wired connection (such as a Universal Serial Bus connection) or through a wireless connection, such as a Bluetooth® connection or other short-range wireless connection. The electronic device 332 may present a graphical user interface through which a user may view temperature and other parameters of the thermal container 300 and may interact with the control circuit 318 to adjust one or more parameters, such as a temperature setting of the thermal tank 308.

The thermal container 300 may include a power supply 330, which may be coupled to the circuitry including the multiplexer 322, the control circuit 318, the I/O interface 324, the sensors 320 and 321, the keypad 328, and the display 326. In some embodiments, the power supply 330 may include a battery. In some embodiments, the power supply 330 may include a power circuit configured to convert power from an outlet into a direct current power supply to the various components. The thermal container 300 may also include a power monitor 334 coupled to the power supply 330 and to the I/O interface 324 (or to the control circuit 318). In some embodiments, the power monitor 334 may provide a signal indicating a power level of the power supply, which signal may be used to control a light emitting diode (LED), a speaker, or another element to provide a detectable indication of the power level. In some examples, the power monitor 334 may cause an LED to light up, to flash or may provide data that can be provided to the display 326, which may be indicative of the state of the power supply 334.

In certain embodiments, the control circuit 318 may control the pump 316 to drive thermal fluid from the cold fluid reservoir 314 through the tubes 315 and 317 into the thermally conductive tube 306, through the tube 307 into the thermally conductive tube 312, and through tube 313 back into the cold fluid reservoir. The tubes 306, 307, 312, 313, 315, and 317 and the cold fluid reservoir 314 and pump 316 may form a sealed, closed-loop system through which the thermal fluid may flow without directly contacting the contents of the cold source reservoir 302 and without directly contacting items within the thermal tank 308.

FIG. 4 is a block diagram of an apparatus 400 including a thermal unit 402, which may be inserted in an enclosure 404, in accordance with certain embodiments of the present disclosure. In some embodiments, the thermal unit 402 may include the control circuit 318 coupled to the pump 316 and to the heating element 336. The control circuit 318 may also be coupled to the temperature sensors 320, the power monitor 334, and the I/O interface 324. The control circuit 318 may be configured to selectively control the heating element 336 to radiate heat via a heating ribbon or strip 432, which may be flexible and which may extend into the enclosure 404. The control circuit 318 may be configured to selectively control the pump 316 to circulate thermal fluid from the thermal fluid reservoir 314 to the cold source reservoir 302 and through tubing 307, a portion of which may extend into the enclosure 404. In some embodiments, the tubing 307 may include a first portion 406, which may be wrapped about a surface of the cold source reservoir 302. The tubing 307 may also include a second portion 408, which may extend within the enclosure proximate to items to be cooled and which may be flexible.

It should be understood that the thermal unit 402 may be an embodiment of the cooling and heating features of the thermal container 300 in FIG. 3, except that the thermal unit 402 may be a stand-alone apparatus. In this example, the thermal unit 402 may be inserted into a thermal container, such as a cooler made by another company, and the second portion 408 of the tubing 307 and the heating ribbon or strip 432 may be extended within the enclosure proximate to the items to be maintained at a selected temperature.

In some embodiments, the control circuit 318 may compare a temperature of the enclosure (determined from temperature sensors 320) to a temperature setting received from the I/O interface 324 and to a threshold. In some embodiments, the control circuit 318 may selectively activate one of the pump 316 and the heating element 336 or may selectively deactivate the one based on the comparison. Other embodiments are also possible.

In some embodiments, the second portion of the tubing 307 and the heating strip or ribbon 432 may be coated with an antibacterial coating to prevent bacterial contamination of items to be chilled or heated. In some embodiments, the control circuit 318 may utilize multiple thresholds or temperature ranges to maintain the temperature of the enclosure within a temperature range of the selected temperature.

In some embodiments, the ambient temperature may be lower than the selected temperature of the enclosure. In some embodiments, the controller 318 may be coupled to an ambient temperature sensor, such as temperature sensor 321 in FIG. 3. The controller 318 may selectively activate the heating element or the cooling element based on a change in temperature over time and based, at least in part, on the ambient temperature. Other embodiments are also possible.

FIG. 5 is flow diagram of a method 500 of operating a thermal container, in accordance with certain embodiments of the present disclosure. At 502, an input corresponding to a temperature setting is received. The input may be received from a computing device (such as a smart phone or other computing device) or from a touchscreen or keypad type of interface provided on a surface of the thermal container.

At 504, the method 500 may include determining a temperature associated with a thermal tank. The temperature may be determined from one or more temperature sensors associated with the thermal tank. In a particular embodiment, at least one of the temperature sensors may be a radiant temperature sensor configured to determine an ambient temperature of the thermal tank based on the air temperature. In an embodiment, the radiant temperature sensor may include a black-globe type of thermometer or another type of temperature sensor configured to measure a temperature of the thermal tank.

At 506, the method 500 may include determining if the temperature is greater than a temperature setting. If the temperature is greater than the temperature setting, the method 500 may include selectively controlling a pump to increase circulation of a thermal fluid from a dry ice reservoir through tubing to the thermal tank, at 508. The method 500 may then return to 504 to determine a temperature of the thermal tank.

Returning to 506, if the temperature is less than the temperature setting at 506, the method 500 may include selectively controlling the pump to adjust a flow rate of the thermal fluid 510. In some embodiments, the pump may be controlled to slow, stop, or even reverse the flow rate of the thermal fluid 510.

In an alternative embodiment, the method 500 may further include determining if the temperature falls below a second threshold. The second threshold may be a temperature that is an offset or delta from the temperature setting. For example, the second threshold may be calculated from the selected temperature (T_(SET)) as follows:

T _(Threshold) =T _(SET) −ΔT   (1)

where the delta (ΔT) defines a range relative to the selected temperature. If the measured temperature falls below this calculated threshold, the control circuit may slow, stop, or reverse the flow of the thermal fluid to warm the thermal tank. Other embodiments are also possible.

FIG. 6 is a flow diagram of a method 600 of operating a thermal container, in accordance with certain embodiments of the present disclosure. In some embodiments, the method 600 may include determining a temperature associated with a thermal tank, at 602. The temperature may be associated with an enclosure of a thermal container, such as an insulated cooler or with a thermal tank sized to fit within the enclosure. Other embodiments are also possible.

The method 600 may further include determining if the temperature of the thermal tank is greater than a selected temperature, at 604. If the temperature is greater than the selected temperature, the method 600 may include controlling a pump to circulate a thermal fluid between a cold source and the thermal tank to cool the thermal tank, at 606. If, at 608, the temperature of the thermal tank continues to be greater than the selected temperature, the method 600 returns to 606 to control the pump to circulate a thermal fluid between a cold source and the thermal tank to cool the thermal tank. Returning to 608, if the temperature is less than the selected temperature, the method 600 may include deactivating or adjusting the pump to adjust circulation of the thermal fluid, at 610. The method 600 may then return to 602 to determine the temperature associated with the thermal tank.

Returning to 604, if the thermal tank temperature is less than the selected temperature 604, the method 600 may include determining if a difference between the selected temperature and the tank temperature is greater than a threshold, at 612. If not, the method 600 returns to 604 to determine if the thermal tank temperature is greater than the selected temperature. The loop presented by 604 and 612 allows the thermal tank to stay within a temperature range until the ambient temperature either cools the thermal tank to a temperature that is outside of the temperature or heats the thermal tank to a temperature that is above the selected temperature.

At 612, if the difference is greater than the threshold, the method 600 may include controlling a heating element to warm the thermal tank, at 614. In some embodiments, the heating element may be a wire, a strip, or another component configured to radiate heat in response to an electrical signal. In some embodiments, the heating element may be controlled by a control circuit (control circuit) configured to maintain a temperature of a thermal tank. At 616, if the thermal tank temperature is greater than the threshold and less than the selected temperature, the method 600 may deactivate the heating element at 618 and may return to 602 to determine the temperature of the thermal tank. Otherwise, if the thermal tank temperature is still outside of the temperature range, the method 600 returns to 614 to control the heating element.

In some embodiments, a thermal unit may be configured to maintain an internal temperature of a thermal tank or enclosure at approximately a selected temperature by selectively applying heating or cooling. In a particular embodiment, a control circuit of the thermal unit may maintain the temperature within a pre-determined threshold range of the selected temperature. In some embodiments, the thermal unit may be installed in a thermal enclosure defined by a portable cooler. In some embodiments, the thermal unit may be integrated in a portable cooler housing. Other embodiments are also possible.

In conjunction with the thermal containers and methods described above with respect to FIGS. 1A-6, a thermal unit may include a cold source reservoir, tubing and a pump configured to deliver a cooling effect to a selected area. The thermal unit may further include a heating element configured to deliver a heating effect to the selected area. The thermal unit may further include a control circuit coupled to the pump and to the heating element and configured to selectively control at least one of the pump and the heating element to maintain the selected area at a desired temperature. The thermal unit may include one or more temperature sensors coupled to the control circuit. Further, in some embodiments, the thermal unit may include an interface, such as a touchscreen, a keypad and display, a transceiver, or another interface accessible by a user (either through touch or via an external electronic device, such as a remote control, a smart phone or other computing device) to configure temperature settings. In some embodiments, the interface may provide information including a temperature, power supply information, and other information.

In some embodiments, the thermal unit may be installed into an existing cooler, such as a portable cooler that can be carried or that can be moved about on wheels. In some embodiments, the thermal unit may be installed into a cooler enclosure within a vehicle, such as a fishing boat, a car, or another form of transportation. In some embodiments, the thermal unit may include a thermal tank having a smaller volume than the internal volume of a standard thermal container, but which may provide a larger volume for securing items to be chilled because the cooling source may be separate from the thermal tank. When a standard thermal container is filled with ice, the ice may occupy a large portion of the available volume. By separating the cooling source from the thermal tank, the volume of the thermal tank may be used exclusively to secure items to be chilled. Moreover, the items to be chilled may be isolated from the cooling source, reducing contamination from bacteria or other contaminants, which might otherwise be floating with the melted ice in the cold water.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. 

What is claimed is:
 1. A thermal container comprising: a thermal tank; a cold source reservoir; a tube forming a closed loop in contact with the thermal tank and with the cold source reservoir and configured to secure a thermal fluid, the thermal fluid having a freeze temperature that is below zero degrees Celsius; and a pump coupled to the tube and configured to circulate the thermal fluid between the cold source reservoir and the thermal tank when a temperature of the thermal tank exceeds a selected temperature.
 2. The thermal container of claim 1, wherein the thermal fluid comprises propylene glycol.
 3. The thermal container of claim 1, further comprising a control circuit coupled to the pump and configured to control the pump to adjust a flow rate of the thermal fluid flowing through the tube based on a difference between the selected temperature and the temperature within the thermal tank.
 4. The thermal container of claim 3, further comprising: one or more temperature sensors coupled to the control circuit and configured to determine a temperature of the thermal tank; and wherein the control circuit is configured to adjust the flow rate based on the temperature.
 5. The thermal container of claim 4, further comprising: an interface coupled to the control circuit and accessible by a user to configure a temperature setting; and wherein the control circuit is configured to adjust the flow rate based on the temperature relative to the temperature setting.
 6. The thermal container of claim 1, wherein the cold source reservoir defines an enclosure sized to receive a piece of dry ice having a temperature of approximately −110° Fahrenheit.
 7. The thermal container of claim 1, further comprising a heating element coupled to the thermal tank, the heating element configured to apply heat to the thermal tank when the temperature falls below the selected temperature by more than a threshold amount.
 8. The thermal container of claim 1, further comprising a reverse flow valve that may be controlled to reverse fluid flow from the thermal tank to the cold source reservoir when a temperature of one of the thermal tank and an ambient environment falls below a threshold temperature.
 9. An apparatus comprising: a thermal unit sized to fit within a portable thermal container defining an enclosure, the thermal unit including: an interface to receive a selected temperature; one or more temperature sensors; and a control circuit coupled to the interface and the one or more temperature sensors, the control circuit configured to selectively control one of a heating element and a cooling element to maintain a temperature of the enclosure within a range of the selected temperature.
 10. The apparatus of claim 9, wherein the heating element comprises at least one of a wire, a ribbon, and a strip configured to radiate heat in response to a control signal from the control circuit.
 11. The apparatus of claim 10, wherein at least a portion of the heating element is flexible.
 12. The apparatus of claim 9, wherein the cooling element comprises: a cold source reservoir; tubing forming a closed loop, the tubing including a first portion coupled to a surface of the cold source reservoir and including a second portion; and a pump coupled to the tubing and configured to circulate a thermal fluid through the closed loop based on control signals from the control circuit.
 13. The apparatus of claim 12, wherein the second portion of the tubing is formed from a flexible material.
 14. The apparatus of claim 12, wherein the cold source reservoir comprises a dry ice reservoir.
 15. The apparatus of claim 9, wherein the interface comprises at least one of a touchscreen, a display and a keypad.
 16. The apparatus of claim 9, wherein the interface comprises a transceiver configured to communicate with a computing device.
 17. An apparatus comprising: a container defining an enclosure; a thermal unit sized to fit within the enclosure, the thermal unit including: an interface to receive a selected temperature; one or more temperature sensors; and a control circuit coupled to the interface and the one or more temperature sensors, the control circuit configured to selectively control one of a heating element and a cooling element to maintain a temperature of the enclosure within a range of the selected temperature.
 18. The apparatus of claim 17, wherein the cooling element comprises: a cold source reservoir; tubing forming a closed loop, the tubing including a first portion coupled to a surface of the cold source reservoir and including a second portion; and a pump coupled to the tubing and configured to circulate a thermal fluid through the closed loop based on control signals from the control circuit.
 19. The apparatus of claim 17, wherein the heating element comprises the heating element comprises at least one of a wire, a ribbon, and a strip configured to radiate heat in response to a control signal from the control circuit.
 20. The apparatus of claim 17, wherein the interface to receive a selected temperature includes at least one of a Universal Serial Bus interface and a wireless transceiver interface configured to communicate with a computing device to receive the selected temperature. 